1. Field of the Invention
This invention relates generally to a transceiver array employing beam-forming and, more particularly, to a transceiver array employing digital beam-forming that includes a plurality of vertically integrated semiconductor wafers.
2. Discussion of the Related Art
Transceiver arrays are widely used in wireless communications, radar applications and sonar applications. A transceiver array is an array of transceiver channels each including an antenna where the channels combine to provide a directional beam for both transmitting and receiving purposes, including beam scanning. As the directivity of the array increases, the gain of the array also increases.
Various types of transceiver arrays are known in the art that provide beam steering. One known transceiver array type includes mounting individual transceiver front-end channels on a mechanical device that moves to provide beam steering or scanning.
Another known transceiver array type is a phased array. A typical phased array includes an antenna in each channel that is connected to a phase shifter, and a power combiner for adding the signals together from the antennas. The phase shifters control either the phase of the excitation current of the antenna for transmission or the phase of the receive signals. When the signals are combined, a beam is formed in a particular direction. Particularly, a transmit beam is formed in space, and a receive beam adds coherently if the signals are received from a particular region of space. The radiation pattern of the transceiver array is determined by the amplitude and phase of the current at each of the antennas. If only the phase of the signals is changed and the amplitude of the signals is fixed, the beam can be steered.
The known transceiver arrays of these types are typically expensive, bulky, consume a relatively large amount of power, etc.
In order to alleviate some of the disadvantages of the known transceiver arrays, digital beam-forming systems have been developed in the art that eliminate the need for the phase shifters to provide beam steering. The digital beam-forming systems digitally provide beam steering. One advantage of digital beam-forming is that once the RF information from each channel is captured in the form of a digital stream, digital signal processing techniques and algorithms can be used to process the data in the spatial domain.
Digital beam-forming is based on the conversion of the RF signal at each antenna into two streams of binary base-band signals representing in-phase and quadrature-phase channels. The digital base-band signals represent the amplitude and phases of signals received at each antenna in the array. The beam-forming is provided by weighting each digital signal from the channels, thereby adjusting their amplitude and phase so that when they are added together they form the desired beam. Thus, the linear phase weight applied to the digitized signal at each channel can make the antenna beam appear as if it is steered to different angular directions.
FIG. 1 is a schematic block diagram of a known transceiver array 10 including a plurality of channels 12 where the array 10 employs digital beam-forming. Each channel 12 includes an antenna 14 that transmits the signal at the desired frequency or receives a receive signal. A transmit/receive module 16 is electrically coupled to the antenna 14 and operates in both a transmit mode and a receive mode. As is well understood in the art, the transmit/receive module 16 includes various components to perform the transmit and receive functions, such as low noise amplifiers (LNA) for amplifying the receive signal, power amplifiers for amplifying the transmit signal, a mixer for converting the transmit signal from an intermediate frequency signal to a high frequency signal and converting the receive signal from a high frequency signal to an intermediate frequency signal, and various filters for filtering the desired frequency, such as band-pass filters and low pass filters. The array 10 also includes an analog-to-digital converter (A/D) 18 that converts the receive signal to a digital signal. A digital-to-analog converter would also be provided to convert the digital transmit signal to an analog signal. The transmit and receive signals are weighted by a weighting junction 20 to provide the beam-forming, and the signal from each channel 12 is summed by a summer 22. A digital signal processor 24 provides the digital signal processing.
As mentioned above, each transmit/receive module 16 includes a plurality of components. Typically, the components in the transmit/receive module 16 are discrete integrated circuit components mounted to a printed circuit board. Because so many components are required in the transmit/receive module 16, the size of the array 10, the component insertion losses and power consumption are significant.